Air blast circuit breaker and control therefor



Dec. 4, 1945. w. M. SCOTT, JR

AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR 8 Sheets-Sheet 1 Original Filed Dec. 21, 1940 Dec. 4, 1945. .w. M. SCOTT, JR 2,390,333

AIR BLAS T CIRCUIT BREAKER AND CONTROL THEREFOR Original File'd Dec. 21, 1940 8 Sheets-Sheet 2 INVENTOR.

BY Z 7 2 i 4 ATTORNEY.

Dec. 4, 1945. w. M. SCOTT, JR 7 2,390,333

AIR BLAST CIRCUIT BREAKER AND CONTROL THEHEFOR' Original Filed Dec. 21, 1940 8 Sheets-Sheet s BYW.W

ATTORNEY.

Dec. 4, 1945. w. scarf JR 2,390,333

AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR Original Filed Dec. 21, 1940 8 Sheets-Sheet 4 mvEm'oR.

BY Z

ATTORNEY.

Dec. 4, 1945. w. M. SCOTT, JR

AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR 8 Sheets-Sheet 5 Original Filed Dec. 21, 1940 F'IG.9.

i HHHH az FIG.

F w J a h INVENTOR. BY 4mm" "1. M 4 z W ATTORNEY.

Dec. 4, 1945. w. M. SCOTT, JR

AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR Original Filed Dec. ,21, '1940 8 Sheets-Sheet 6 INVENTOR.

ATTORNEY.

1945- w. M. SCOTT, JR 2,390,333

AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR Original Filed Dec. 21, 1940 8 Sheets-Sheet 7 ATTORNEY.

Dec. 4, 1945.

w. M. SCOTT, JR

AIR BLAST CIRCUIT BREAKER AND CONTROL THEREFOR Original Filed Dec. 21, 1940 8 Sheets-Sheet 8 lI!!!ll/rill!ll/IIIIIIIIIIl/llll/ I a 1 1 a l:

n-p-unnuu disconnected; This} htwet Patented Dec. 4, 1945 UNITED STATES PATENT OFFICE Vania Original abolic'at on' Dece'ii'ilii-Zi, 1940: Serial No. 3711792. Div ded and'th s applica'tlon'Jan vary 4; 1944, Serial No. 516,917

This invention" relates" iii geh'raI" to the field of circuit interrupte'rs' and 1 more sjiecific'ally concerns a circuit breaker and a control circuit therefor, particularly adaptable to: the p "ate-ction of mercury arerectifiersanu tueir assecistd 'cir'cuitsa This appiidatiofi" le a di'vis'iori' of my I'parent application Serial No. 3711092; filed December 21, 1940.

The anodes of a mercury arc rectifier are in general operated frdmtne 16W voltage side of a. multiphase transformer which; in turn, is usually fed from a three' 'phase alternating current power'supmr. Tlie'niir'iiber of anodes employed is dependent I tifion the particular installation} but in general the rectifiermay" contain 6, 12 or 24 anodes with thedire'ct' current load circuit joined between the neutral point of'th'e transformer connection and the mercury pool cathode.

The protection" r mercury" arc rectifi'trs 1 and their" associated circuits concerns itself primarily with the instantaneous interruption of fault c'urrents which occur as a result ofback' fires and other internal rectifier failures. The exact nature of back fires, internal short circuits and other electronic faults are not completely understood and the means for'pr'e'cluding the occurrence of such faults during rectifier operation have not been completely develo oed.

Upon the establishment of a back fire fault, current flows between the unaffected anodes, the cathode and the back firing anode. The secondary of the transformer feeding the rectifier circuit is thus effectively short-circuited.

The'magnitude oi the current flowing in the circuit of the back firing anode may attain dangerously high values and the damage caused thereby may be extreme. This is particularly true in installations where several rectifiers are operating in" parallel orwhere the rectifier direct current'bus' is connected to generative apfrjaratus which can cause current to flow into the bus; as for example, a direct currentshunt motor.

Under these circumstances, the direct current flowing from the ca-thodetothe affected anode through-the rectifier may cause the'destruction of the anode or of the transformer secondary.

Several methods maybe utilized fo'rcontrolling the ficw of current under the'above notedcircumstance'sj Thus the alternating currentsunply feeding the transformer primaries" may be r1 still permits the flow direct current rom the cathode" of the rectifier-"to the affected anode from any of t h'e aforementioned parallel rectifier's or generative equipmentjolned thereto.

'I'heflow of currentmay also be controlled by disconnecting the direct current bus from the cathode of the rectifier by means of circuit" interrupters-inserted therein. But this willstill perniit the'flow of alternating current between the unaffectedanodes and the back firing anode.

Therefore; to-efiectiv'ely clear the circuit of'the fault, it is necessary to have an extremely'high speed circuit'breaker operate instantaneously to disconnect the alternating current supply'from the affected anode: This interrupts the flow of both the'alternatlng and direct current through the" affected 'ano'd'e'.

My invention contemplates ahi'gh speed single pole circuit breaker for connection in the anode leadsof a'mercury arc rectifier. The single pole circuit breakers requiredfor all of tlieano'des are interlocked by acomm'on switching and control system including a common source ofac'tuating energy'as, forinstarice, c'ompressed air;

Upon theest'ablishmeirt of the 'back fire or similar fault; the rapid increase in current iii-the afiected" anode" circuit operates instantaneously to'tr'ipthean'ode' breaker and to initiatean air blast for extinguishing'the'arc established'therein. It is obvious that a single pole circuit breaker will operate upon the establishment of a fault to inter'rup't'theaifec'ted circuit in less time than a mechanically interlocked multipole' breaker;

Thus'the singlepole anode breaker whic'h'is in the affected circ'uit will operate" with a' minimum'- of time delay to interrupt the fault currents flowing therein. My'novel control system'interlocks all of' the single pole circuit breakers" by non-mechanical means, that is, the individual circuit breakers are interlocked by" meansof a plurality" of compressed airmanifol'ds and elect'ri'cal circuits;

The instantaneous 'ober'ationof' a single anode breaker to remove a fault current will energize the tripping rfie'ansof the anode breakers and thusth'e' oiie'ration of a single breaker will cause a corresponding ober'ation of I all of the breakers.

However; the" essential feature isth'e immediate operation of the circuit breaker in the anode circuit which may be carr ing many times the rated current there'o'fi while the other anodes may not be carrying excessive currents.

It" has been observed that if a" back firinganode in' a mercury arc rectifier is instantaneously disc'onnected andthe current interrupted and then immediately reinserted into the circuit, normal operating conditions frequently they be restored.

Therefore, in mercury arc rectifier installations, in order to avoid a complete shut down of the operating equipment upon the occurrence of an anode circuit fault, there is therefore provided an interlocking system in which the automatically tripped circuit breaker does not affect the circuit breakers in the unaffected anode leads.

Upon the complete interruption of current flow in the affected anode, the circuit breaker in the affected anode lead is reclosed. If operation in this manner restores normal conditions, then the direct current load will be maintained with but relatively small ripple in the line'voltage for the duration of the temporary back fire. This is extremely desirable in instances where shutdowns clue to mercury arc rectifier back fires may inconvenience the users of the direct rectified current.

However, it is quite possible that the fault may not be one of a temporary nature. that is, inc stantaneous interruption and reconnection may not operate to remove the faulty condition and of course, the affected circuit breaker will continuously operate to open and reclose the circuit breaker contacts.

Therefore a counting or t me delay device may be included in the control system for the individual anode poles and may be interlocked with the control systems of the other circuit breaker poles so that after a circuit breaker pole has opened 1:

a predetermined number of times due to a faulty anode condition. the dev ce w ll actuate the interlocking tripp ng mechan sm to isolate all of the anodes from the multi-phase transformer and effectively isolate the mercury arc rectifier.

Should the fault condition cease to exist before the affected anode Circuit breaker had opened and re-closed its predeterm ned number of times, the other poles would remain closed and the counting device would automatically reset for a future operation.

The control system also includes a means for indicating the number of automatic operations in each'circu t breaker in order that faulty operation of any one anode maybe read ly determined and resettable means are included for indicatin which of the poles last operated.

The high speed circuit breaker which I have devised comprises a pa r of cooperable contacts upon which a directed high velocity ar blast may operate to cause contact disengagement and are extinction with a minimum of time de ay. A diaphragm valve in each of the anode circuit breakers s the air blast control element and all of these valves are interlocked by means of a manifold in a manner such that automat c tripping of a single pole or manual tripp ng of all poles may be obtained. The interlocked diaphragm valves serve, in addition, to protect the main air storage tank so that the ent re charge of air contained there n wi l not be lost during a circuit breaker interru t on.

Reclosing of the breakers is automatiaclly obtained if the circuit breaker opening has been a result of a, temporary mercury arc rect fier fault such as a back fire, but closure of all of the rectifier poles is obtained by having another interlocked control system which in this instance is an air manifold joining the reclosing means of all of the anode breakers.

It is therefore an object of my invention to provide a high speed single pole circuit breaker, particularly adapted for operation in the anode lead of a mercury arc rectifier.

Another object of my invention is to provide means for effectively interlocking a plurality of single pole circuit breakers.

, Still another object of my invention is to provide a plurality of circuit interrupters which are effectively interlocked; which interlocking permits independent operation of a single pole when required by the circuit.

A still further object of my invention is to provide a circuit interrupter which operates to interrupt single anode faults without necessarily disconnecting the entire rectifier from the circuit.

Still a further object of my invention is to provide a circuit interrupter which will interrupt momentary faults due to backfires in mercury arc rectifier operation and which will isolate the mercury arc rectifier if a permanent fault has occurred therein.

It is still a further object of my invention to interlock the plurality of Single pole anode circut breakers by means of a compressed air opening and reclosing system and a plurality of electrical switch ng devices for operating the same.

These and other objects will become apparent from the following spec fication taken in connection with the accompanying drawings. in which Figure 1 is a broken cross-sectional V ew of a single pole circuit breaker and the means for interlocking the same with a plurality of similar poles.

F gure la is an enlar ed view of part of the circut breaker shown in Figure 1.

Figure 2 is a fragmentary View of one of th control switches operable by the circuit breaker taken alon the line 2-2 of Figure l.

Figure 3 is a cross-sect onal view of a single pole circuit breaker taken along the line 33 of Fig ure 1.

Figure 4 is a fragmentary cross-sec ional view of the over oad ma net and adjus ng m ans therefor taken along the line 4-4 of Figure 1,

Figure 5 is a broken cross-sectional View of the circuit breaker tripping manifold taken along the line 55 of Figure 1.

Figure 6 is an enlarged cross-sectional View of the check valve operable within the air manifold along the line fi-6 of Figure 5.

Figure '7 is a supplementary view of the check valve taken along the line 1-1 of Figure 6.

Figure 8 is a cross-sectional View of the single pole circuit breaker indicating the involute air passage surrounding the circuit breaker contacts taken along the line 8-8 of Figural.

Figure 9 is an end sectional View of the circuit breaker taken along the line 9-9 of Figure 1,

Figure 10 is an end cross-sectional View of the circuit breaker taken along the line lfi-l0 of Fi ure 1.

Figure 11 is a fragmentary cross-sectional view taken along line "-r-II of Figure 10.

Fi ure 12 is a schematic representation of the plurality of anode circuit breakers and the control means therefor.

Figure 13 is a schematic representation of one modification of the controlling system of Figure 12.

Figure 14 is a fragmentary schematic view of a counting system operable for circuit breaker control.

Figure 15 is a schematic representation of a six-phase mercury arc rectifier and the corresponding number of single pole circuit breakers in the anode leads thereof.

Figure 16 is a fragmentary schematic view of the over current magnet and illustrates one form of polarizing coil for reverse current tripping.

In Figure 1 there is shown a single pole circuit breaker which is one element of a plurality of interconnected poles operable within the anode leads of a mercury arc rectifier. Figure 15 schematically indicates a typical installation which in this instanc includes a six-phase mercury arc rectifier employing in each of the anode leads, a circuit breaker element of the type indicated in Figure 1.

The rectifier anodes are fed from a six-phase star connected secondary 2| of a transformer, the delta connected primary 22 of which is fed from a three-phase alternating current transmission line. The center tap 23 of the six-phase secondary is connected to the negative terminal of the d rect current transmission line and the mercury pool cathode 24 is the positive terminal thereof.

The six anodes 25 within the mercury arc rectifier are each jo ned to .a corresponding anode lead from the six-phase secondary and a single pole circu t breaker is inserted in each of these leads, as will hereinafter be indicated. The plurality of circuit breaker elements employed are interconnected to effect the desired circuit interruptions for mercury arc rectifier operation.

In Figure 15 there is shown a typical backfiring condition. Current from each of the five normal anodes flows through the faulty anode 25 and results in a heavily overloaded anode circuit. In addition to the sum of all the alternating current components, a d rect current. which is schematical y indicated by the feathered arrow. flows through the affected anode. This component may be except onally great if the direct current circ it comprises generative apparatus.

If, for instance. the direct current load comprises a shunt motor 26. as is schematically illustrated, or additional mercury arc rect fiers in parallel. or a paralleled direct current generator. the direct current will be the result of the current which th s apparatus may supply throu h the low impedance transformer secondary and the relatively low impedance arc from the cathode to anode 25. This component; of the fault may there ore be particularly destructive to the anode and the correspond ng transformerv secondary.

As has hereinabove been pointed out, a cathode protective breaker 21 which is in series with the direct current transmission l ne may be tri ped to remove the direct current component that fiows through the faulty anode. This however, will not preclude the fiow of excessive alternating currents therein.

A current interrupter in the anode ci cuit of the rectifier w ll operate to remove both alternatin and direct currents and iso ate the rectifier. But s nce a single anode is particularly overloaded. an independently operating single pole circuit breaker will best be suited to relieve the fault cond t on with a minimum of time delay. This individual breaker may be caused, during internotion. to actuate the tripping mechanism of all other anode breakers to result in the ultimate isolation of the rectifier.

The exact nature of the single pole circu t breaker and of the tripp ng and control means therefor will now be described and reference is now made to the cross-sectional views of the single pole breaker, Figures 1 and 1a.

The single pole of the circuit breaker illustrated consists essentially of two cooperable contacts 3| and 32. and means for d recting nd controlling an air blast which enters through the pipe 33 and passes over the separated contacts during circuit interruption. The plurality of circuit breakers which are required for the various rectifier anode leads may all be mounted directly upon a common storage tank to shorten and thus facilitate piping connections thereto as indicated schematically in Figure 12. That is, the base 34 of the flange 35 may be coupled by bolts or other suitable mean directly to an air storage tank which is charged by means of a compressor. The systems may be adjusted so that pressure therein remains within predetermined limits and that any variations of pressure outside of these limits may operate to open the circuit breakers.

The main metallic casting 36 of the circuit breaker is, as will hereinafter be shown, at a relatively high potential and it is therefore necessary to electrically isolate the casting from ground potential. Therefore, the casting 36 is supported upon the air storage tank by means of a pipe 33 made of a suitable insulating material and of sufiicient length to ensure a minimum of leakag and to preclude the possibility of an arc between the circuit breaker frame and the air storage tank.

The base of the casting 36 is preferably a circular external flange 31 which is supported upon the pipe 33 and thus upon the air storagetank by means of the piping flange 4| which i in screw thread engagement at 42 with the insulating pipe 33. The external flange 31 of the casting 36 may then be fastened to the piping fiange by any convenient means, as for instance, a plurality of machine screws, but first an annular gasket 43 is inserted therebetween to-preclude the leakage of air at the junction of the surfaces.

A tapered opening 44 of diameter equal to the inner diameter of the insulating pipe 33 admits to the casting 36 air which is then conducted through the cored passage 45 to the controllable diaphragm valve 46.

The cored passage 45 terminates in an annular air passage 41 which completely surround the diaphragm valve 46. Aligned with the valve is a projecting circular pipe 5| which provides a passage 52 for directing the incoming air to the contacts 3| and 32.

The end surface 53 of the inwardly projecting pipe 5| is smoothed to cooperate with a layer 54 of valve seat material which is carried by the valve diaphragm 46.

The passage 52 provided by the annular metallic projection 5| which has been integrally molded into the casting 36 is more clearly illustrated in Figures 3 and 8 wherein it may be seen that the passage 52 is a cored involute, spiralling to completely surround the contact 3| as indicated in Figures 1 and 3.

Thus air enterin into the passage 52 will be conducted to the contact 3| and the air stream will completely surround the contact.

Returning now to the air control means, that is, the diaphragm valve 46 illustrated in Figure 1, it may be seen that air fiow in the cored passage 52 is controlled by the position of the valve seat material 54 relative to the edge 53 of the inwardly projecting pipe 5|.

The valve diaphragm is supported upon the metallic casting 36 in a counter-bored recess 55 in the wall of the casting. The diaphragm 46 is a circular piece of flexible material such as rubber and is held in the counterbore 55 by means of a circular dome shaped member 56 which is turned down at 51 to correspond with the inner diameter of the counter bore 55.

The dome shaped member 56 is then securely fastened to the main casting 36 by means of e plurality of machine screws it which are circularly disposed as: is a more clearly indicated in the rear view (Figure 51- of the dome-shaped member 56-.

The machine screws 6 l passthrough atcorresponding. set of perforations 62 in the dome shaped: member and engage threaded preforations,6.3- within thema-in casting=36.-. The valve diaphragmas is thus'securely, clamped between the; projection: and the maincasting 36: In order to assure an air tight joint at t-hispoint and to prevent.radial-"movement of the edge of the diaphragm when:subjectedto airfpressure, a, wedge shaped circularprotrusion: 64 on' the projection 51" is forced into 'the resilient material of the diaphragm when thescrews -6 l are tightened. Thermember 56:-has beenamachined to provide the spherical dome E5" and thusaxialdisplacemerits of the diaphragm 46" arelimitedtoth'e space between the dome. 85'; and" the end 53 of the'inwardly projecting i coredpipe 5L TheiVa-lve diaphragm 5% is. of flexible material andhas'secured to it two circular metallic disks 66 and'fiz'l omeitherside'of the fiexiblematerial. The face of v dish 611' is'facedvJith a valve'seat'imaterial. 54 which: will provide a suitably close surface engagem nt with the end 53 of the inwardly'projecting passage; The four layers of material therefore-which comprise the movable portion on the. valve are bound togetherr'by thescrew T l and itsassooiated nut l5 which assists-"in directing theflow of air. toward; the discharge: when theT-valve i's'open.

The rear face 14 of the metallic} disk- 66 has been: machined to correspond withv the: dome shaped chamber 65.- Thus it maybe seen that the inflowing air which enters through the insulating pipe 33 is guided to the annular cored passage l! surrounding the inwardly projecting pipe El and the face of the diaphragm valve. Ifnew the diaphragm 46 is displaced to the left, as viewed in Figure 1', the air will, as indicated by the arrow heads of Figure 1 ent'erfrom the passage 45' and passage 4-! into the tapered and spiralled passage 52 which supplies air to'the contact engaging surfaces. Therefore, actuation of the diaphragm valve 45 will control the circuit breaker blast and will be"discussed in greater detail in later paragraphs inasmuch as the structural details of the circuit breaker will now be described.

Contact 31 is a conically shaped butt contact engageablewith a nozzle shaped contact 32 along the contact surfa'ces'3l" and 32 which have been faced with a suitable conta'ct'material such as a non-weldingv alloy of tungsten and silver, silver and graphite, or the like. w

Nozzle shaped. contact '32 is. fixed relative to the mainframeiiifi of the circuit breaker. whereas contact, 31- isslidable relativethereto. As indicated in Figures 1 and 3, contact 3| has been displaced from its closed position: and thus the air flow is indicated by the arrowheads. Asthe blast air approaches the contacts through a spirallyshaped passage 52, as indicated in Figure 8, the airflow about contact 3| will be in the form of a vortex while passing outwardy through nozzle. shaped contact 32. Therefore, an are which is drawn between contact faces 3| and 32 as a result of contact separation will be spun about the contact surfaces. This action will facilitate cooling and decrease the possibilities of contacts 3! and 32" Welding. The spinning air exhausting between the contact surfaces and through contact 32. isillustrated schematicallyby thearrow headsin-Eiguresl and 3;

Nozzle. shapedcontact 32 is. supported within a circular. opening, 15 which. is. formed" within a projectingextension 16 of the maineastingfli;

As willibepoint'ed outin later paragraphs,, the main frame 36 is at the potential of. contact 3i and. therefore it is. necessary to l support contact 32 within the opening 15 by suitablemeans of insulating material. Contact 32 is. secured between-the line terminal 11 and the. exhaust pipe and. muffler 8' I and 82,. This. assembly is made rigid byv an. external fiange83l'onthe outer end of contact. 3 2- nesting: within counterbores 84 in terminals 11 and 85. in exhaust pipe. Bl so. that when the. parts are assembled. as indicated. in Figures l and. 3,, the contacts 32 will; be rigidly held therebet'w'een.v I

The entire. assembly is maintained in fixedrel-ation by means of. a plurality of studs. 86. extending from terminal LT and. passing. through corresponding, perforations 8LT within the flange endofthe exhaustpipefil. Thisis. more clearly indicated. in. Figure 10. where the. approximately square fiangedendoi the exhaust pipe. illisillustratedas carrying. in. the. corners thereof. the plurality of. nuts 9t whichasin-FiguresLand 3 serve tocIamp-the exhaustpipe to the terminal 7:? which is alsoindicatedin.Figure 10. V

The assembly of contact. 32,.terminal HI and exhaust pipe 81. is then. clamped to. the main casting 36. by means-of a plurality ofssocket head screws 92-. more clearly indicated in-.Fignres l0 and: 11. That. is, line terminal llprovides. a series of perforationseii through wlzlich.the. socket head screws 22 may pass. intoacorresponding tapped perforation 9:4. in the main casting. 36..

It has beenpreviously pointed out. that. it. is essential to insulate. line terminal. 11- from the mainframe. 36 inasmuch as-frame 36: is. at the potentialv of contact 3L and: line terminal. 1:1: is at the.- potential of oontact32i. Therefore, the soeket'headscrews 92'have been sheathedin in sulation; that'is, a cylindrical tube of-insulation 95' has been provided to prevent the shank of the bolt from contacting terminal. 1.! and the head of the bolt: has. been similarly, protected by a; cylindrical cup 96. which has-been perforated at- 91 to? allow the passage of. the insulating tube 95: V

It should be noted that if desirable; the various tubes of insulating material may be dispensed with if the socket head screws orv other types of. screws employed to bind the assembly of contact 32, terminal H- and exhaust'pipe 81 to the main frame 36 are made of. a sufficiently strong insulating material;

Prior to. theiinsertion of. bolts 92- intos-th'e. main frame 36; a plate H of insulating material'is placedth'erebetween and isperforated: at H12 in order to correspond with all of the insulating cylinder I03; contact32 will project, into-the'passage I and .will be centrally located with respect to the spirally oriented air passage .52.

It should be noted that the outer cylindrical surface of the contact 32 has been turned down at I05 to provide an .air gap I08 between the insulating tube I83 and the faceofthe contact 32 which is at the potential of line terminal TI. This, in effect, provides an increased leakage path and therefore reduces the possibility of electrical break-down at this point.

The nozzle shaped passage I01 of the contact 3.2 provides for the expansion of the blast airin order to reduce back pressure.

Exhaust pipe BI juxtaposed against-contact 32 along the face III provide iatapering passage which is acontinuation of the tapering passage of the low pressure side of the nozzle. .Thepipe supports, by means of the screw threads M2, the hollow cylindrical muffier .82 and the ,deionizing stack II3. This stack comprises a plurality of parallel metal laminations over which the hot arcproductspass and are eifectivelycooled.

Conical contact 3| is mounted upon a piston I I4 which is'slidable Within a cylinder I I5 in the main casting .33. In order to prevent leakage of air over the piston I4, a'series of grooves H5 have been turned in the piston and piston rings or other packing may be inserted therein.

The contact 3I is centered on the piston .I.I4 by a boss extending into a perforation Ill and is clamped thereto by means of the screw threaded plunger rod I2I. This rod has been turned down and threaded at ,the end I22 which engages a tapped perforation in the contact 3|. By tightening these threads, the vannular flange I23 is brought intocontact with a flexible conductor I24 which has been perforated .at 125 toallow the passage of the plunger rod .I2I. Therefore, bringing-plunger rod I2I into screw thread engagement with the perforation in 3I will securely clamp the assembly of contact 3I,.pist.o-n I.I.4.,and flexible conductor I24.

The movement of piston ,I I4 is limited bythe engagement of contact faces ,3I.and ,32'at one end of the stroke (at which time the circuit is i closed) tothe engagement of the rear faceof the piston with .a ring shaped rubber or otherflexible washer E26 which has been secured within areentrant flange !.2'|',.molded into themaincasting 3,6. As indicated in Figure 3, the outer edge of this flang has been cut away at .I3I to allow for the passage of the flexible conductor I24.

:Piston II-4 therefore which is operable within the-chamber II,5 between the limits of engagement with 'the stationary contact and the annular rubberring I26, is the operating element of the circuit breaker, that is, operation of the piston H4 in either direction by means of air pressure controlled by diaphragm valve 46 or any of the other valves which will hereinafter be discussed, will operate either to open or close the circuit.

Contact M is connected to the external circuit through the flexible conductor I24 which allows movement without in any way impeding movement ofthe piston. The flexible conductor I24 is composed of a series of highly conductive metal laminatio-ns stacked together by suitable means and is. fastened at ither end to a bifurcated member by means of the plurality of machined screws I32. The bifurcated member I33 then continues downward to engage the line terminal I34 and the cable- I35 from theexternal. circuit by means of the bolt or other fastening means I35,

Supported by theflange I21 isa member MI which positions the plunger rod I2I. The mem ber I4I contains a cylinder 1in WhiCh'iS P able a piston I43 and it associated ,packing I"4i4 mounted on the end of .the plunger.

Secured in one end of the cylinder I42 a flanged bushing I 5I whichin this embodiment is fastened by the screw thread 132. A perforation I53 allows the passage of :the plunger rod but this perforation is within a re-entrant flange 154 .for reasons which willbe pointed out in a following paragraph.

.A flange ,1 55 on the plunger ro'd 'I2I which originally had been machined circular similar to the flange I23 is milled off so'that'it may engage the rectangular. cross-section of a .U -shaped channel I56 asindicated in Figures land-'3.

Thepiston I43 is drilled at I51 to allow the passage of plunger rod I2I whichisthen clamped thereto'by means of the nut 16],. iPrior to the application of the nut, however, a-series of ,fiber or other type ,of washers I44 are slipped over the plunger rod Ill and .thus when cla'rnped-bynut IIiI provide the necessary airtight packing -=for piston I43. The iU-shaped channel 156 is held between the flange I55and the piston I43 and'is allowed to extend out :through the axialperforation I152 in member 'I4I so thatit may cooperate with the switchin member "I 63 which will'hereinafter be described.

Contact L3I is biased normall-y towards-the open position, that is, .the position corresponding to contact'between the rear of the piston IHand the shock absorbing memberI26. Thisis accomplishedby .means of a compression spring 484 p which is lodged between the -re-entrant flange I54 previously described and theflange *I55 which supports the U-shaped channel. As the spring is normally under compression, and as the reentrant flange I54 .is fixed, there is a tendency to draw contact 3| from-engagement with contact 32.

The outer end of theclosi-ng cylinder casting is provided, at itslower edge, with a pair of horizontal lugs I39. 'Thebifurcated"-member 138, which is also the over-current bar, is supported against'th 'bottom of these lugsbystuds threaded into the bar, passing through holes in the 'lugsandheld in position by nuts and lock washers I T5. "The lower end of-the baris braced by the member 'I83'as will be described in afollowing paragraph.

The forked conductor-I33 supports-upon aprotrusion, .the plurality of machine screwsfll which pass through magnet laminations l ll. Thee-magnet is composed of stacked soft iron or other magnetic laminations'each of which is fhorseshoe shaped'and as such surroundsthemagnet bus bar I33 (see -Figure 4) .whic-hisanintegral extension of the forked member 133. ".As it :is desirable to preclude the possibility .of icurrent flowing through the magnet, ::the screws .HI are insulated by .means of iinsulating shea hs I15 which completely surround their respective screws.

.Referringnow'to Figure-4whicnis-a cross-sectional .view of the magnet'andmagnet bus jbar 115.3, it :may be s en that themagnet \bus passes directlythrough the fhorsershoe. shaped. ma net formedby the stacked laminations. .The ,arma- .ture IIB ofthis magnet is, a trapezoidal laminated bar of magnetic material which. is car d- 31 a plunger I'II.

Theoperation of the magnet may beexplained briefly by noting that ,theline current will flow through the bus bar indicated in'Figure 4, and

' bolts I85 to the magnet bus.

will establish a 'cylindricalmagnetic field surrounding ,the conductor itself. Therefore, the stacked laminations comprise a magnetic circuit for the flux in the vicinity thereof and accordingly the faces I8I and I82 act as magnet poles and exert a force of attraction upon the wedge shaped armature I16.

It is frequently desirable particularly in the protection of the anodes of mercury arc rectifiers, to cause circuit interruption upon the flow of small reverse currents. This may be accomplished by means of a polarizing coil upon the magnetic structure as is illustrated in the simplest possible form in Figure 16.

Here a coil or plurality of coils I89 surrounding the magnetic structure is continuously energized by a constant voltage. The force exerted upon armature I16 due to the flux of this polarizing coil is in the same sense as the force which will be exerted by the flux produced as a result of reverse current flowing through bus bar I13.

The polarizing flux alone is insufficient to cause displacement of armature I16, but may be adjusted so that relatively small reverse currents will result in actuation thereof to open the circuit breaker. The application of a polarizing coil does not prevent normal operation of magnet upon forward currents.

As indicated in Figure 1, the magnet bus I13 which may, during short circuit periods carry considerable currents, is braced so as to preclude any mechanical deformation thereof due to the stresses developed by virtue of the magnetic forces. The brace comprises the metallic member I83 which has been fastened by means of machine screws I84 to the frame of casing 36 and by means of the plurality of machine screws and This brace is insulated from the flange 31 by insulating layer I89 however, the brace itself may be formed from an insulating material.

.. The electromagnetic device I12 in conjunction with the armature I16 controls the diaphragm valve 46 to control the admission of air to the contact chamber. The plunger rod I11 operates under the influence of the magnet I12 and in order that the rod I11 be maintained in alignment, it passes through a perforation I86 within the magnet lamination stack and through a perforation I81 in the magnet bus bar I13.

The armature I16 is clamped securely to the rod I11 between the flange I19 and nut I9I which engages a series of screw threads on rod I11. The rod I11 is continuously biased towards the right as viewed in Figures 1 and 4, by means included within the cylindrical member I93.

The cylindrical member I93 is fastened to the main frame 36 through the dome shaped member 56 by means of the screw threads I94 upon both the cylindrical member and a corresponding hollow in the rear of the dome shaped member.

However, inserted into the hollow of the dome shaped member prior to the insertion of the hollow cylindrical member I93, is a small circular metal piece I95 which contains a conical valve seat I96 and a cylindrical perforation I91 to permit the passage of air from the diaphragm valve. The conical projection of the circular metal member I95 provides for surface engagement with a layer of valve seat material 26I which is embedded in a metallic disk 202 which is integral with the end of the rod I11.

the inner wall-of the hollow cylindrical member I93 so that it is maintained central at all times.

The hollow cylindrical member I93 is terminated by a metal stop 203 which is fastened thereto by means of the engaging screw threads 264 and which isperforated centrally at 265 to permit the free operation of rod I11.

It should be noted that bearings are provided for rod 111 by the perforations within the bus bar and in the metal stop 263. The biasing means for rod I11 is obtained by springs acting between the metal disk 202 and stationary members. Thus a small diameter central spring 266 bears against both the inner face of disk 202 and the inner face of the metal stop 293. This'spring is of relatively small diameter and fits over the rod I11 which thus acts as a guide therefor.

A second and adjustable spring 291 bears against the. inner face of the disk 292 and also against a movable or adjustable guide 2| I. The guide 2 is a ring shaped metallic member having a perforation 2I2 of diameter large enough to pass over the spring 206 but small enough to provide a, seat for the end of the spring 291. The ring 2 is slidably fitted within the hollow cylindrical member I93 and is adjusted therein by means of a plurality of fins 2I3 which project through axial slots 2I4 in the walls of the cylindrical member I93.

These fins may comprise merely two pins which have been embedded in the ring shaped member 2I I and project from the axial slots 2 I4. As both spring 206 and spring 201 are continuously under compression, there will be a tendency to move disk 292 and its attached rod I11 to the right as viewed in Figure 1. The magnitude of this tendency is controllable by means of the adjustable nature of spring 261. That is, by threading the outer surface 2I5 of the hollow cylindricalmember I93 and passing a nut 2I6 thereover and in engagement with the threads 2I5, the fins 2i3 may be displaced axially upon rotation of the nut 2I6. Thus the compression of spring 261 will vary with the position of nut 2 I6.

Obviously, therefore, the variation in the compression forces of spring 291 will accordingly vary the biasing force of rod I11 and its asso-- ciated magnetic armature I16. As will be indicated in the following, the magnet I16 when operated controls the operation of contacts SI and 32. Accordingly, an adjustment of either the air gap or restraining force on the armature I16 will correspondingly vary the magnetic forces required to displace the same and thus operate the circuit breaker. This then provides an adjustment for the tripping current required.

Two small control switches are actuated by the rods I63 and I11. The switches as more clearly indicated in Figure 2 are mounted upon insulating brackets such as 2H and 2 iii. The switches operable by their contact carrying rods are essentially butt contact switches employing a metallic bridge to complete the circuit between the two contacts. Thus as indicated in Figure 2, the rod I63 carries the bridging metallic member 22I which is engageable with the two butt contacts 222 and 223.

The rod I63 passes through a perforation 224 within an insulating member 225 and thus is maintained in slidable relation therewith. The

entire'switch is clamped to the insulating bracket so that valve seat material comes into. contact. with the metallic insert I95, the switch 23I is. in.

the closed: circuit position.

When contacts 3i and 32- are closed, current.

flows from the bus. bar or other electrical con.- nection 235 which is bolted tothe line terminal bus 11' by means ofthe bolts 236, through the engaged contacts and then through the flexible conductor I:24 to the tines of the bifurcated mem-.. ber I33, then through the magnet bus bar I13; and=out throughthecable or bus bar I35.fastened thereto.

Under closed circuit conditions and nolelectrie. cal disturbances, the full tank pressure. will exist in the passage- 45 and the annular cored chamber 41 on one side of the diaphragm valve 46. and also in the chamber between the valve- 46.; and thedome shaped member 56-. Under these conditions of equalized unit pressure on both sides, thevalve 56- will be displaced more to the right as viewed in Figure I, inasmuch as the left side of the valve has a considerably larger area than thering-shaped under side of the valve. There-v fore, with equal unit pressures on both sides of the diaphragm, the valve seat material 54 will be forced into engagement with the end of the projecting passage 52 and thus cut off the supply of air to. the involute passage surrounding the contacts.

The contacts 3L and 3-2 are maintained in engagement allowing full air pressure to be estaba lishedwithinthe chamber 236 which will thus actuate piston [M and: rod I21: in a direction I which will close the contacts against the action of the biasing compression spring L64.

However, the removal of valve disk 5,4. from. contact with the projecting pipe 53; will allow full: pressure tov be built up. in the involute passage 52 to. the contacts. 3t and 32'.

From Figures 1 and 3, it may be seen that pis-. ton II4 which. is fixed relative to. contact M is of considerably larger diameter than the piston I43 and therefore without necessarily releasing the pressure in the chamber 233, the contact 3! will be displaced to. the left. as viewed in Figure- 1.

Full tank pzessure is main i d in the h mher 236. by means. of the closing manifold 231' which connects the air from. the storage tank to each of the singlepole circuit breakers controlled therefrom The manifold 231 itself may comprise a Bakelite. tubing performed at 2;4 I to allow the admission of air to and from chamber 236. and the entire manifold as. indicated in. Figure. 3 is supported between two, clamping brackets 242 and 243 which are maintained in fixed relation by means of the plurality of bolts 2 .4 which, in addition, fasten the, brackets to the frame of the circuit breaker.

The nature of the manifold mounting is indicated in Figure 9 which is an end view of the circuit breaker. The clamping action is secured by means of the bolts 244 as previously mentioned which pass through suitable lug-s cast into the clamping bracket 2-42.

The semi-cylindrical depression 245 in the clamp 243 which surrounds the air passage 24I which has been out into the manifold 231 must be lined with a suitable gasket 246 to, prevent leakage therefrom.

The clamping bracket 243. must, in addition to the semi-cylindrical depression 245,, contain a perforation 241 which will allow the entrance of air to the chamber 236.. Again, t prevent air leakage, the surface contact between the clamp ing bracket 24,3- andthe hollowcylindrical mem-v ber l;4.aI must be sealed with. a suitable gasket 25L The blast valve control manifold 255 is supported by means of a semi-cylindrical clamp256 upon a. boss 251 integrally m d on the dome shapfid. member 56, The boss 251 has been machilled to, accommodate the cylindrical manifold Z55.Which is rigidly clamped; thereto by means of th pluralityof bolts 26 I which pass through suitable erforat n n both, he mp and the d m shaped member. The manifold 255 comprises a Bakelite cr -other suitable insulating tubing which is; interconnected with each of the poles of the circuit breaker as will be pointed out in the fol.- ow ns disc s i nlbprevent leakage of airaround the junction of the Bakelite manifold and the semi-cylindrical cut -away in the, boss 251, the semi-cylindrical opening is lined with a rubber or other flexible gasket; 262 as is more clearly illustrated in the enlarged fragmentary view of the tripping maniol F gur 6- The tripping manifold 255 is connected by air passages to the control diaphragm valve 46 and the valve 201 which is operated by the electromagnetic device I 16. A perforation 263 in the tripping manifold is connected by means of the duct 264 to the nozzle I91, formed in the metallic disk I55, which forms the seat for the valve disk 26I.

The cylindrical opening I91 and the conical tapering opening I96 have, in addition, been joined to the inner portion of the dome shaped member 56 by means of a circular array of holes 265 and thus duct 264 is effectively interconnected with the space between the dome shaped member 56 and the diaphragm valve 46, whether the valve 261 is open or closed. The portion of duct 264 projecting into the nozzle-shaped opening in: disk I95 has been designed so that an as-pirating effect is secured when the air flows through duct 264 and through opening 191, to draw the air through holes 265 when valve 261 is opened.

An additional air passage is provided from the manifold to the dome space by means of a duct 266, more clearly illustrated in Figure 6, and the flow of air through this duct is controlled by a check valve 251 formed. in the rubber gasket 262. As seen in Figure 5, this duct is displaced sideways from duct 234 The duct 266 leads into the manifold 255 through a rectangular or other relatively large perforation 211 which has been formed therein. It should be noted from Figure 6 that the perforation 21I is relatively large when compared to the duct 256.

This valve is formed by cutting two parallel slits 212 into the gasket on either side of the duct 26.6 as indicated in the fragmentary View of Figure '1.

The diameter of the larger perforation 211 in the manifold is greater than that of the spacing between the two slits. Therefore, when the pressure in the manifold 255 is low, as compared with the pressure of the air within the dome, there will be a tendency for the air to flow, as indicated by the arrow heads in Figure 6, in a manner such that the flexible material contained between the slits 212 will bend as indicated and thus allow air to passv around the slits and into the manifold.

On the other hand, if the pressure in the manifold 255 is greater than the pressure within the dome, there will be a tendency to force the flexible; material, between the slits, up against the smaller duct 286 and thus efiectivelycheck the flow of air through the duct. The reasons for this arrangement will be taken up in the following paragraphs.

When the circuit breaker is connected in circuit with the anodes of the rectifier as in Figure 15, and all the poles are closed, the individual poles are interconnected by the manifolds 231, and 255, and full tank pressure will exist in both manifolds. Therefore, as full tank pressure also exists in the passage and in the annular chamber 41, the diaphragm 46-will be moved as determined by the side having the greater surface area.

This obviously is the side which is adjacent the dome shaped member 56 as the area of the valve disk covering the blast pipe is at atmospheric pressure. Full tank pressure exists between diaphragm 45 and the inner wall of the member inasmuch as this chamber is connected with the tripping manifold 255 through the duct 254 and the plurality of perforations 265. It should be recalled that for normal conditions of operation (that is, valuesof current up to the current for which the armature is adjusted) that the valve 2GI is normally biased to engagement with the disk I95 and therefore the air within the dome and within the tripping manifold does not escape. Should a fault occur on the anode to which the pole under discussion is connected, the armature I15 would be actuated to the left as viewed in Figure 1 under the influence of magnet I12, and the valve 2iil will be removed from surface engagement with the disk I95.

This will immediately allow the air contained within the dome to exhaust through the plurality of openings 265 and through the nozzle shaped opening I91. This air will pass to the outer atmosphere through the guide fins around the valve Elli and then through the perforations 2M within the wall of the hollow cylindrical member I83.

In addition to this escape air which is flowing through opening I91, air will flow from the tripping manifold through the duct 264 and out through the opening I91. Inasmuch as this outflowing air is at a high pressure, means must be provided to prevent it from reducing the velocity flow from the dome through this passage. The aspirating effect has been arranged in order to increase the velocity of the air flowing from the dome. High pressure air cannot enter the dome through the duct 266 because the check valve 261 effectively blocks any such flow.

A reduction in pressure within the dome will immediately allow the full air pressure contained within the chamber 41 to actuate diaphragm valve 46 to the left as indicated in Figure 1 and accordingly allow the main air blast entering from the tank, upon which the breaker is mounted, to flow into the involute passage 52. The increase in pressure within the passage 52 will operate upon the relatively large diameter piston H4 and will thus force contact 3I to the left against the action of the high pressure air upon the small diameter piston I43.

Immediately thereafter an arc will be drawn between contacts 3I and 32 which will be extinguished by means of the high velocityair blast which is in this instance a rotating or spinning air blast.

The heated air will exhaust through the nozzle shaped contact 32 and its associated extension SI. Upon flowing through the mufller 82, the air stream will be cooled by the stock H3 which,

as previously described, comprises a parallel stack of spaced metal plates.

During the operation of the circuit breaker under the influence of an overload or fault current two other important operations are performed in the following sequence. First, upon the actuation of magnet armature I'iii, the switch 23! is opened, and second, immediately following the displacement ofcontact (H to the left, the contacts of switch 221 are closed.

The position of the armature I76 is determined by the current flowing through the magnet bus bar I13 and therefore immediately following current interruption, the force upon armature I16 will vanish and therefore the armature I16 will again be solely under the influence of the biasing springs 205 and 2N.

The springs will carry the valve disk 20I into engagement with the metallic member I95. It is important to note that the springs 205 and 20? must supply sufficient biasing force to close the valve although rull tank pressure exists within the opening let. The reclosure of valve 2th will, through oucts 25 3 and the plurality of openings 265, cause the pressure to the rear oIXdiaphragm 86 to build up to the fulltank pressure whereupon the diaphragm valve will immediately close and thus out on tnesupply of air Iiowlngtnrough the involute passage 52.

This precaution has been taken to preclude the possibility of the air stored within the tank from completely discharging through the chamber 52 and its associated exhaust passages. Again, assuming that no other external influences have acted upon the circuit breaker, the removal of the air supply from chamber 52 will effectively decrease the pressure therein and accordingly if the full pressure still exists within the closing manifold 231, air will flow to operate the piston I43 and its associated piston rod Ml to the right as viewed in Figure l to close contacts 3| and 32 and thus complete the circuit which had been interrupted by means of the automatic electromagnetic tripping device I12.

The cycle of events described immediately above concerning the operation of the circuit breaker under the influence of an overload assumed that the pressures in the two manifolds 231 and 255 remained at the storage tank value.

The nature of the changes occurring in the pneumatically operated control system will now be described with reference to the operation of a series of single pole circuit breakers, each of which is in circuit with an anode "of a mercury arc rectifier.

The complete control system for a circuit breaker of which Figure 1 is a typical example, comprises means for manually and automatically completing the circuit to all of the anodes simultaneously. In addition, it contains a plurality of protective features such as under pressure tripping mechanism and may be arranged so that each circuit breaker may through a counting system open and reclose a predetermined number of times prior to the opening of all the poles of the circuit breaker.

The control system schematically illustrated in Figure 12 shOWs a plurality of poles such as those of Figure 1 insulatedly mounted upon a main storage tank 30I which is illustrated in elevation and in section. This storage tank is maintained at a pressure within predetermined limits by means of an air compressor.

The six single pole circuit breakers, which have the numerals 302-301 but to facilitate the fol lowing description of the operation of the controlling system, the pole 301 has been drawn to be a diagrammatic representation of the pole of Figure 1.

In carrying over the reference numerals applied in .Figure 1, the current enters the pole 301 through the bus bar 235 which is jointed to the contact 32 mounted upon an insulator IOI within the main casting 36. Cooperating contact 3I is mounted upon a piston II4 which is in turn in operative relation with smaller diameter piston I43 through rod I2I. From contact 3I the current is carried by the flexible conductor I24, by bar I13 through the horse-shoe magnet I12, and thus to the bus bar I35.

The armature I16 is in operative relation with the magnet I12 and is carried upon the plunger rod I11 which in turn carries the valve 20I. The diaphragm valve 46 controls the air stream entering through chamber 45 to passage 52 which surrounds the contacts. The tripping manifold 255 communicates with each of the domes formed between member 56 and the diaphragm 46; and the closing manifold 231 communicates with each of the closing cylinders and associated piston I43.

The switches 221 and 23I are operated by the plunger rods I2I of the breaker contact and Ill of the armature respectively. The circuit breaker 301 is illustrated as tripped and having been caused to remain open. However, it should be noted that the valve 20I has been closed and that therefore diaphragm 46 has been displaced under the influence of air entering the dome from the manifold 255 to shut off the blastair.

Air is supplied to the tripping manifold 255 through a tap 3II from the main storage tank through an electromagnetically operated valve 3I2. The members 3I3 at each of the poles represent the junction between the manifold 255 and the diaphragm valve 46 of each of the poles. The control system is electrically operated from a direct current source which may be copperoxide rectifiers, batteries or the like, and has been schematically illustrated by the battery 3 I2.

The valve 3I2 is controllable by means of the electromagnetic device which in Figure 12 is schematically illustrated as a plunger type solenoid 3I5 which in the circuit indicated is operated by two parallel switching and control systems. One of these control lines originates at the negative control bus bar and contains in series therewith the plurality of switches 221 each of which is operated by the piston rod I2I of its associated circuit breaker.

From the plurality of series switches 221 the electrical circuit then passes through relay 3I6 and solenoid 3 I and then terminates at the positive bus bar. A second circuit also originates at the negative control bus bar and then contains three switches in series: switch 32I which is the hand trip, switch 322 which is the underpressure automatic trip, and switch 323 which is an interlocking switch. These three switches and their specific functions will be described in later paragraphs.

In series with these three switches are the plurality of switches 23I one of which is mounted upon each of the circuit breakers. At the termination of these switches, the control line extends to the positive bus through the relay 3I6 and the solenoid 3 I 5.

There are, therefore, two parallel circuits for controlling the relay 3 I 6 and the solenoid 3 I 5, and

either circuit will be effective for the energization thereof.

Each circuit comprises a plurality of switches in series. Therefore, if one or more switches in each of these circuits are opened, the relay and solenoid will be de-energized. When all of the circuit breakers are closed, the corresponding switches 221 are all in their open position and the control of the relay and solenoid depends solely upon the normally closed switches in the other circuit. Upon the opening of all the circuit breaker poles, a circuit is completed through all the switches 221 for purposes to be described later.

Solenoid 3I5 when in the energized position as indicated in Figure 12 allows passage or air from tank 30I to the tripping manifold 25,5 and thus permits the entry of air into the space between the dome shaped member 56 and the diaphragm valve 46. However, when in the de-energized position, the schematically represented plunger 324 will be actuated by the spring 325 to allow the high pressure air within the tripping manifold 255 to exhaust through the indentation 326 contained therein. The operation of solenoid 3I5 will not permit the escape or air through the coupling 321 within the valve and time will not pclllllt mic LSca c UL all. soured wlcllnl ullc: Main.

The closing manifold 23! utilizes the compressed air of the storage tank 3M taken at the tap 3H througn the pipe 331. An electrornagnetically operated valve 332 controls the influx of air thereto and when the solenoid 330 is in the oe-energized position as indicated in Figure 12, the air contained within the closing lllallllold. 231 is permitted to escape through the piping connection 333 and the indentation 334 within the solenoid plunger 335.

The spring 336 is employed to depress the solenoid plunger 335 when the electromagnetic device is de-energized. In the energized position, the perforation 341 within the solenoid plunger permits the flow of air from the tank 31 to the closing manifold 231..

Joined to the closing manifold is a relief valve 342 which may be employed to vent the closing manifold. When this valve is open, accidental closing of the circuitbreaker contacts is impossible.

It is to be recalled from the construction of the single element of the circuit breaker as indicated in Figure 1, that the switching member 221 is open circuited when the contacts 3| and 32 are in engagement and the switching elements 23I contained on each of these elements are in the closed circuit position, during normal conditions.

Therefore, when the circuit breaker is in the closed circuit position, the switches 221 do not control the operation of the electromagnetic device 3i5. If normal conditions prevail, the switches 23l and the switches 32I, 322 and 323 will all be closed and the electromagnetic device 3I5 will be energized and the plunger 324 will be in the position indicated in Figure 12. This allows air pressure to be built up within the tripping manifold 255 which closes the diaphragm valve 46 to prevent the flow of air into the involute chamber 52.

This condition, of course, prevails in each of the individual circuit breaker poles 302-301; If any one of the switches 32!, 322 or 323 are opened for reasons which will hereinafter be described, the electromagnetic device 3I5 will be de-energized and vent the tripping manifold 255 to cause the contacts 355 separate, the coil 354 is de-energized, but the coil 353 remains in circuit. The relay armature 358 is therefore drawn down beyond its normal mid-position against the magnetic pole of coil 353 and held in that position with contacts 36| and 363 open. If, during this condition, the contacts 355 of relay 316 reclose, the

contacts 36I and 363 will remain open despite the re-energization of coil 354. When the switch 35I is released, the coil 353 will be de-energized and the armature will return to its normal midposition.

The relay 3l6 provides an interlock between the tripping system and the solenoid 330 controlling the air pressure in the closing manifold. When the-breaker is tripped, the closing manifold must be disconnected from the storage tank and vented to the atmosphere to prevent reclosure of the breaker contacts when the blast valve diaphragms close.

The coil of this interlock relay 316 is, therefore, connected in series with the coil 3l5 of the tripping manifold valve 3l2 so that they are deenergized simultaneously upon the automatic opening of any breaker pole. This action vents the trip manifold 255 for actuation of all the unoperated blast valve diaphragms, and at the same time, by the separation of contacts 355 deenergizes relay 351.

Thus, the solenoid 330 is de-energized and the pressure in the closing manifold is reduced to that of the atmosphere, assuring that the springs I64 will hold the breaker contacts open.

Upon the opening of all the circuit breaker poles, a control circuit will be established through the switches 221 to re-energize coil M5 and close all the blast valves, which as previously described, will preclude the exhaustion of the storage tank. This action will simultaneously energize relay 3l6 and close contacts 355. Under this condition, as previously described, the relay 351 cannot reclose its contacts 36! and 363, no matter whether the control switch is open or closed. This effectively prevents repeated opening and closing of the breaker contacts when the switch 351 is closed during a fault condition.

As the control system requires that full air pressure be maintained on the closing manifold when the breake contacts are in closed position, the coils 353 and 354 of relay 351 and coil 330 of the air valve are designed for continuous duty. This condition is also true of the tripping system as the coils 3| 5 and 3|6 are deenergized only during opening movement of the breaker contacts.

It is frequently possible and desirable in the operation of certain polyphase circuits, to permit the interruption and immediate reclosure of a single pole of the circuit breaker without necessarily interrupting the other poles thereof. More particularly, it has been found that internal rectifier faults such as backfires may be cleared by merely opening and reclosing the affected anode circuit, while permitting normal operation of the unaffected anodes.

In order to provide for such an arrangement within the control system illustrated in Figure 12, it is necessary to preclude the operation of one of the switches 23l immediately upon the occurrence of an overload. Yet it is necessary to actuate switch 231 to interrupt all of the poles if the anode fault is permanent in that it cannot be removed unless the mercury arc rectifier is shut down and repaired.

Figure 14 illustrates one modification of a devic which may be mounted upon the circuit breaker illustrated, which functions to permit a single pole to open and reclose several times before the entire mercury arc rectifier is taken out of operation.

In order to modify the circuit breaker in accordance with Figure 14, it is necessary to remove each of the switches 23| from its fixed relation with shaft I11, which carries the armature I16 of the electromagnet I12.

Attached to the end of the shaft I11 in place of the switch 23 l, is a pawl 31! biased by means of spring 312 into engagement with a ratchet 313. In addition, the locking devic 314 is biased into cooperation with ratchet 313 by means of spring: 315 which may be pinned to the frame of the circuit breaker.

The occurrence of an overload will displaceshaft I11 to the left as viewed in Figure 14 and in: conjunction with the pawl 31! and the locking: device 315 will rotate the ratchet 313 through an angle as determined by a single notch thereon.

A lever 316 which is fastened to the ratchet by means of the screw 311 is positioned to operate a switch 38! which occupies the same position as switch 23l in the control circuit of Figure 12.. Therefore, a number of operations of shaft I11 due to repeated circuit overloads will continuously rotate ratchet 313 until lever arm 316 opens switch 36l to open circuit all of the circuit breaker poles in a manner described in connection with the operation of switch 23 l.

A single overload occurring in. one of the poles will move the ratchet one notch, vent the dome behind the diaphragm to open the single breaker, and due to the biasing action of the springs about shaft 111, the circuit breaker pole in which the fault occurred will reclose immediately following circuit interruption.

The number of successive interruptions which may be allowed before all of the poles are interrupted may be predetermined by suitably positioning the lever arm 316.

The system as indicated in Figure 14 provides a number of cycles prior to the interruption of the entire mercury arc rectifier anode circuits and is cumulative in its operation, that is, if several cycles of opening and immediate reclosing are required to clear an internal rectifier backfire, and if similar backfires occur later in the operation of the rectifier, the ratchet 313 will again progress several notches and thus after several backfires or several instantaneous circuit interruptions, the ratchet will have progressed sufficiently to actuate the switch 38| and interrupt all of the circuit breaker poles. Thus, an anode which is frequently giving trouble will eventually cause the rectifier to be shut down.

In the above device, subsequent to the interruption of all of the circuit breaker poles, it is necessary to readjust or reorient the ratchet 313 in order to reset lever 316 to its original position. In order to overcome this inconvenience, the modification illustrated in Figure 13 may be employed.

In this modification, each of the switches 23l is in circuit with a solenoid 382 through a parallel circuit of an annunciator 383 and an electrically operated counter 384.

In this modification, the switches 23! have been removed from the control circuit in series with the tripping solenoid 3I5 and have all been replaced by a single switch 39| which is in operative relation with the solenoid plunger 385, through a notching mechanism as will now be explained.

This series circuit is connected across the ter-- minalssofi a: direct current vcontrol'lcircuit such'asi' I thebattery 31.4 of, Figure; IZFand'thusfollowing:

the actuationof any of the switches 23!, thesole noid; plunger 385 will operate upwardly aszviewed in Figure 13. l

The closure ofone of the switchesz23i: Will actuate: the: lever 38-3, of I the annunci'ator about its arm 395: in fixed relation thereto. A pawl 396- whichis p-ivotally mounted upon the lever arm 392:is biasedinto engagement with the notchesof'ratchet 394'by means of aspring 398 and'thus" rotation of, lever'arm. 392; due to axial displacements of plunger 385. will. cause rotation of the ratchet 393:

A: biasing, spring 391 tends to rotate'ratcliet 393:" in-a direction opposite to that obtained by anzupwardi displacement of plunger 385, and nor mally pulls lever 395 against-a fixed-stop 399i A: locking. device 40L pivotally' mounted upon the. pin 402l.is biased in the direction for: engagement with ratchet 394- and when in engagement therewith will prevent spring 391 from rotatingthe ratchetr However, locking de vicelimlzis normall disengaged-from ratchet 394 b means of the gravitationalefiect of a'pistOn 403 -and piston rod 404,

Piston rod' lfil l lsin alignment withplunger rod1385: and" its" associated piston 403 1 is-"slidably fitted within a cylinder 405" which is vented through an adjustable exhaust 406. During normalioperation-of the circuit breakera-nodes, thesolenoid 382 is: deenergized'and thus the locking device piston and 'ratch'etassumethe positions indicated in Figure 13, wherein it may be seen that the pawl 396 engagesa stop 480*which causes disengagement from ratchet wheel 39 4- and permitsispring 397 to rotate the lever 395 against its step 399.

Energization of'coil' 382*due tothe closureof one-of the switches-2M 335 -andthus rotate ratchet 394 through one-or more notches. In addition, the operationof plunger rod 385 will drivepistonMJ-i up'intothe': cylinder 405 and thusallow lockingdevicelfll to come into engagement with ratchet-394 'to preelude restoration to its original position imme diately upon the de-energizationof coil 382." Therefore, member 395 wil1 remain in a substan tially fixed position until piston 403 and its as sociated piston rod 404 descend-and disengage the locking device 4M from the ratchet'394.

The adjustable small exhaust wfi providesflin? efiect, when combined with-the cylinderandpis: ton a time delay mechanism inasmuch asith'e descent of piston 403 will be relatively slow, As the circuit breaker'operationis similartothat previously described, the-anode pole' which' has been-opened due -to a fault will immediately reclose; If the fault-is still presentwithinthe cir:

cult, the switch- 231 will be-"reclosed immediately and-will again actuate plunger rod 385 to again of lever 392 about-a required will rapidly raise plunger rotate'ratchet see through on'emr more notchesh And?inasmuch as pi'ston 403 has not completed-i its descent, the locking 'device 4fl l willagain pre: 1 clude the return: or the ratchet: to its:- originalposition;

Therefore, it ma beseen sthat repeated opera-'-- tions of the circuit breaker contacts will cause" a continued rotation of ratchet' 3'94 andi at the 'ter mination of the predetermined number'of. cycles,-v the member 395 will open switch 39 l'which; as previously mentioned, isin-th'e control circuit and will interrupt all of the circuit breaker polesi 1 If, on the-otherr'h'and, a: rectifier fault-occurs and" a single-opening and: reclosure is suflicient to'clear this fault, then the delayed descent of piston 4ll3 'would ultimately disengage the lockingl devicettll' from the ratchet 394*- and: permit its return to: its limiting position: when the coil 382: is inthe de-energized position; 7

If the circuit breaker is operating. upon? at per-*- manent rectifier fault, a'succession' of operatioiis will'be required before switch 3'9|is opened.=to* isolate the rectifier: from/the transformersec ondaries.

Subsequent to the interruption, th'e'piston tfll-l Willfdesc'end andfreethe ratchet from theloclringi; device to 'permit spring 391 toreturn the ratchet to its original position.

The entire system, as illustrated in Figuretvl3 will therefore: serve as a countingimecha'nism in order that any of the anodes beiallowedt'o operate; several times before the mercuryarcmectifier is isolated from'the line: In addition, it serves to visually indicate upon which anode 'the fault has occurred, and the total number-of operations of each pole of the circuit breakerz' It is important to note that'lthe systemsnllus trated in Figures-12,13 and l l areieritirelylsche matic, that the valves; solenoids, relays; time delay mechanisms and the like have b'een illus trated in their simplest form merelytofacilitate the. explanation of the systemi involved;

The various rela-ysand other devices required may be of the known cominercial types and need' onlyfunction as the devi'ces'illustrated in order" that they may be applied? to the controlflcircuits It will be evident that many modificatiohs of the above-described circuit breaker design and circuit breaker control-systems may-be madeby those skilled' in the art and thereforeI do not wish to be limited to the specific disclosures fierc inabove set forth but only bythe-scope of tli'e' appended c1a'ims.-

I'claim:

i. In an electromagnetically operatd' valve, a magnet excited by avariable current-in a' conductor associated therewith; a valve element comprising an" armature associated with" said magnet and i a valve disk; acylindrical' housing comprisingavalveseat and enclosing saidvalvedisc and providing guiding means for said valve" element; a'first valve closingspring surrounding said element-and i pressingagainst said housingand saidvalve disk, an adjustinge1ement-sur=--- rounding said first spring and liaving-arms-ex tending ,th'rough' slots in said li'ousing para-llel'to the axisthereof, a second" valve spring pressin'gagainst said adjusting element-- andsaid valve" di'sk and a member in" screw thread engagement with the exterior of" s-aidF-housing and bearing against said arms:

2; In a fluid operated circuit breakerhaving-a fixed" and a cooperable-movable contact, a-piston rod connectedto said movable contact, means controlled by-a fluid under pressure for operating 

